In general, there are two major types of cotton species being cultivated throughout the world, namely Gossypium barbadense and Gossypium hirsutum. These two species are from the genus Gossypium, which comprises at least 40 different cotton species. Gossypium barbadense (sea island cotton) and Gossypium hirsutum (upland cotton) are allotetraploids and are known as New World cotton or “American” cotton. There are striking differences in the physical characteristics of the cotton fibers produced by G. barbadense compared to the cotton fibers produced by G. hirsutum. G. barbadense produces longer cotton fibers than most other cotton species and these fibers are usually called “extra long staple” (ELS) fibers, while those of G. hirsutum are shorter and are called or defined as “upland” fibers. Textiles made of ELS fibers are considered to be of higher quality compared to textiles made with shorter fibers, like those produced by G. hirsutum cotton plants. Thus, textiles produced from ELS cotton fibers are considered more valuable in the textile marketplace.
Many regions around the world produce ELS cottons with distinct fiber qualities, such as Egyptian Pima and Indian Pima. Despite the common ancestry, over time, isolation and/or cross breeding of a cotton species has created subtle but unique genetic variations in cultivars from different regions. Even though these cotton types belong to the same species, G. barbadense, ELS from certain regions, such as American Pima, have superb fiber qualities compared to G. barbadense grown in other regions of the world and are heavily promoted and highly sought after by textile manufacturers. Thus, certain ELS cottons from a particular geographical region are more valuable than others. All ELS cotton cultivars are within the G. barbadense species, and there is really no physical measurement(s) which can readily distinguish between various ELS cotton cultivars produced from different geographical regions.
Unfortunately, once cotton fibers are processed and made into yarn and/or fabrics, there is no reliable method to determine the origin or cultivar of the fibers utilized to produce the yarn or textile(s). Forging clothing or producing knock-off textile items is a serious problem for the textile industry, costing manufacturers and retail stores millions and perhaps billions of dollars annually, in the United States alone. Some manufacturers are using inferior quality cotton or other cheaper ELS cotton to cut costs. This is not necessarily equivalent to making fake products, but this practice still impacts not only the brand owner but also the cotton producers. Being able to identify the cultivar of a particular species of cotton utilized in a textile item would not only be a way to authenticate an item as legitimate and being made with the type of cotton specified by the owners, but would also enable the detection of forged or counterfeit textile products.
There have been many studies trying to manipulate cotton genes for fiber quality improvement (U.S. Pat. Nos. 6,169,174; 7,060,874; and 6,995,256), enhanced pesticide toxin production (U.S. Pat. Nos. 6,686,149; 6,140,075; and 6,057,370), and herbicide resistance (U.S. Pat. No. 7,223,906). There have also been studies investigating the genetic polymorphism of various cotton species using PCR-based markers (J. Applied Sci. Res. 3(10)1156-1169, 2007). A variety of studies have demonstrated that DNA heterogeneity within strains of similar species can arise both in intragenic (inside) and intergenic (outside) genetic coding regions, and that polymorphism at the level of DNA yields a remarkably specific signature for individuals, strains and species. However, no success has been found in the categorization of cotton cultivars using genetic markers on mature cotton fibers mainly because of the lack efficient primers to amplify fragmented DNA in mature cotton fibers.